The present invention relates generally to sensor technology. More particularly, the present invention relates to sensors comprising one or more electroactive polymers that convert between electrical and mechanical energy; and their use in various sensing applications.
A sensor is a device that detects a change inxe2x80x94or determines the value ofxe2x80x94a physical parameter. Conventional sensors may be classified based upon the parameter they sense. Common commercially available sensors include temperature sensors, pressure sensors, flow sensors, stress/strain sensors, accelerometers, dielectric sensors, conductivity sensors, shock sensors, and vibration sensors.
Conventional sensors may also be classified based upon the transduction mechanisms they employ. For example, a strain gauge measures changes in temperature, pressure, and/or deflection of an object via changes in physical dimensions, or strain, of the strain gauge. There exist many different strain gauge transduction mechanisms. Some simple strain gauges are based on materials capable of generating a voltage when subjected to small deflections. For example, piezoelectric-based strain gauges convert mechanical deflection to an electrical signal for strains in the range of 1 to 2 percent. This minimal deflection range severely limits piezoelectric-based strain gauge usage.
Devices capable of measuring larger strains or displacements are usually much more mechanically complex. Linear potentiometers may detect strain in the range of 1-6 inches or more, but are limited to linear deflections and are bulky, expensive rigid and often have low accuracy; thus restricting usage. Mercury filled elastic tubes are another conventional large strain sensor that is not limited to linear deflection and whose resistance changes as cross-section is reduced during stretching. These devices suffer from cost issues, and the mercury introduces undesirable safety concerns. Another conventional large strain sensor includes a rubberized air bellows of fixed diameter that is attached to a pressure transducer. Additionally, there are complex strain gauges based on changes in inductance of an insulated wire coil and strain gauges based on changes in capacitance of a bifilar helix of insulated wire coils. The complexity and size of these large strain sensor devices often restrict usage in many applications, e.g., when the required device size is small or when the environment does not permit complex mechanical designs.
In view of the foregoing, an alternative form of sensor for detecting a parameter would be desirable.
The present invention relates to sensors and sensor systems that comprise one or more electroactive polymer transducers. Each transducer comprises at least two electrodes in electrical communication with an electroactive polymer. The transducer is configured such that a portion of the electroactive polymer deflects in response to the change in a parameter being sensed. The electrical energy state and deflection state of the transducer are related. The change in electrical energy or a change in the electrical impedance of the transducer resulting from the deflection may then be detected by sensing electronics in electrical communication with the transducer electrodes.
In one aspect, the present invention relates to a sensor for detecting a change in a parameter. The sensor comprises a transducer including at least two electrodes in electrical communication with an electroactive polymer. The transducer is configured such that a portion of the electroactive polymer deflects in response to the change in the parameter and the deflection produces an electrical change in the transducer. The sensor also comprises sensing electronics in electrical communication with the at least two electrodes and designed or configured to detect the electrical change.
In another aspect, the present invention relates to a method of using an electroactive polymer transducer which comprises at least two electrodes in electrical communication with an electroactive polymer. The method comprises applying a voltage difference between the at least two electrodes. The method also comprises deflecting the electroactive polymer from a first position to a second position. The method additionally comprises detecting an electrical change in the transducer resulting from the deflection from the first position to the second position.
In yet another aspect, the present invention relates to a sensor for detecting a change in a parameter. The sensor comprises a transducer including at least two electrodes in electrical communication with an electroactive polymer. The transducer is configured such that a portion of the electroactive polymer deflects in response to the change in the parameter and the deflection produces a capacitance change in the transducer. The sensor also comprises sensing electronics in electrical communication with the at least two electrodes and designed or configured to detect the capacitance change.
In still another aspect, the present invention relates to a sensor for detecting a change in a parameter. The sensor comprises a transducer including at least two electrodes in electrical communication with an electroactive polymer. The transducer is configured such that a portion of the electroactive polymer deflects in response to the change in the parameter and the deflection produces a resistance change in the transducer. The sensor also comprises sensing electronics in electrical communication with the at least two electrodes and designed or configured to detect the resistance change.
In still another aspect, the present invention relates to a sensor for detecting a change in a parameter. The sensor comprises a transducer including at least two electrodes in electrical communication with an electroactive polymer. The transducer configured such that a portion of the electroactive polymer deflects in response to the change in the parameter and the portion deflection produces a resistance change in the electroactive polymer. The sensor also comprises sensing electronics in electrical communication with the at least two electrodes and designed or configured to detect the resistance change.
In still another aspect, the present invention relates to a sensor for detecting a change in a parameter. The sensor comprises a transducer including at least two electrodes in electrical communication with an electroactive polymer. The transducer is configured such that a portion of the electroactive polymer deflects in response to the change in the parameter and the deflection produces a resistance change in one of the at least two electrodes. The sensor also comprises sensing electronics in electrical communication with the at least two electrodes and designed or configured to detect the resistance change.
In another aspect, the present invention relates to a sensor array for detecting a change in one or more parameters. The sensor array comprises at least one transducer. At least one transducer comprises at least two electrodes coupled to a first portion of at least one electroactive polymer. The at least one transducer is configured such that the first portion deflects in response to a first change in the one or more parameters and the first portion deflection produces a first electrical change in the at least one transducer. At least one transducer also comprises at least two electrodes coupled to a second portion of the at least one electroactive polymer. At least one transducer is also configured such that the second portion deflects in response to a second change in the one or more parameters and the second portion deflection produces a second electrical change in the at least one transducer. At least one transducer also comprises sensing electronics in electrical communication with the at least two electrodes coupled to the first portion and in electrical communication with the at least two electrodes coupled to the second portion. The sensing electronics are designed or configured to detect the first and second electrical change.
These and other features and advantages of the present invention will be described in the following description of the invention and associated figures.